These 2 charts compare Zonal Wind anomalies (reds are Westerly Wind Bursts) and Sea Surface Temperature anomalies through June of their respective years. 2015 appears not as strong in terms of the number and coverage of the WWBs, and total warm water accumulation in the East Pacific could be debated as being not as warm. But coverage in the Central Pacific in 2015 is larger. This is attributable to 2015 starting out with an already warm from the false start El Nino in 2014, where 1997 was coming out of a La Nina like pattern. But overall the patterns are similar. It appears the debate at this time will be whether the character of the WWBs in 1997 (less in number but broader in areal coverage and duration) will ultimately push a greater volume of water east resulting in a stronger El Nino signal as compared the WWB pattern so far in 2015 (more episodes but less coverage and duration).